1. Field of the Invention
The present invention relates to anticoagulative high-molecular compositions, more particularly, high-molecular compositions having an anticoagulative property which comprise as the main component a cellulosic polyelectrolyte complex formed from a polycationic cellulose derivative and a polyanionic cellulose derivative.
2. Description of the Prior Art
Hitherto, various plastic materials have been used in the field of medical instruments or devices such as various kinds of catheters, cannulae, tubes, blood-stocking containers, injectors, etc., as well as artificial internal organs, external circulation-aiding apparatuses and the like. The biggest problem encountered with the known materials was that the materials caused coagulation of blood as they came into contact with blood. Although it is known that such blood coagulation results from the contact of a blood protein called "contact factor" with the surface of an alien substance, the particular mechanism of the coagulation is still not clear. Therefore, it is not well known at the present time what types of materials are anticoagulative.
At present, the following three methods are used to obtain anticoagulative materials:
(1) Synthesizing high-molecular materials provided with those features which are considered favorable to anticoagulative properties,
(2) Adding or bonding an anticoagulative, physiologically active substance to or with a synthetic material, and
(3) Preparing a medical instrument with a living body per se.
Method (3) is, for example, a method of extracting and grafting an endothelial layer which is prepared by burying a high-molecular material in the body of an animal. However, the method is difficult to carry out on an industrial scale.
Method (2) is, more particularly a method of blending or bonding heparin, a water soluble polysaccharide functioning as an anticoagulative which is present in the body of animals, with a high-molecular material. However, it is difficult to maintain the original anticoagulative activity of heparin, probably because the functional groups of the heparin are partially consumed by the process of bonding the heparin with the surface of the high-molecular material. Moreover, such method is poor in productive and processing abilities. Also in the case of blending, heparin is not effective unless it appears on the surface of the material and, on the other hand, heparin present on the surface of the material is easily eluted, and so there arises a problem that coagulation is insufficient on bleeding or that the maintaining of coagulative activity for a long time is difficult.
Thus, it is most desirable to obtain anticoagulative materials by the synthetic method (1). However, there are no known materials, which meet the requirements of having those properties which are considered favorable to anticoagulative activity, such as suitable hydrophilic/hydrophobic balance, surface electric charge, etc., that they should be easily processed on molding, that they should have good affinity for blood, and that they are not dissolved or eluted, in or by blood.
It has now been found by the inventors of the present invention that polyelectrolytic cellulose complexes, which can be formed by mixing a polycationic cellulose derivative and a polyanionic cellulose derivative in a solvent common to the two, are insoluble in water and blood and have an excellent anticoagulative property. Cellulosic polyelectrolyte complexes are known to be effective for hair-dressing in the form of solution, though they are not yet isolated (U.S. Pat. No. 4,299,817 is referred to).